This question has been answered clearly since the early 1970s by the collective voices of scientists all over the world. As described in the Background section of this website, experts concluded in the early 1970s that cellulosic biomass could be used as additional new feedstocks besides food crops for ethanol production. However, it was found that most types of cellulosic biomass contained two major fermentable sugars, glucose and xylose. Unfortunately, xylose could not be used by the Saccharomyces yeast for growth or for the production of ethanol. In the early 1980s, the global scientific community realized that it might not be possible to isolate naturally occurring yeast to effectively ferment xylose to ethanol. As such, scientists worldwide began to genetically engineer the Saccharomyces yeast to ferment ethanol.
The most important reason for using yeast to produce ethanol is that yeast performs this task very efficiently under acidic, low pH conditions. Under these conditions, no toxic microbes can survive, propagate, and contaminate the production. For more than a thousand years, humans have employed yeast to produce wine or ethanol using a range of methods – from primitive techniques to very sophisticated industrial technology. To this date, no hazardous incidents have ever been reported.
The following are additional reasons why yeast should be used to ferment sugars from cellulosic biomass to ethanol:
- It has been the microorganism traditionally used for industrial ethanol production.
- Proven robustness in industrial fermentation processes.
- Well accepted by industry.
- Co-products can be used as animal feed or for other applications.